Coating agent based on a branched hydroxyl group-containing polyester-modified polyacrylate resin and use thereof

ABSTRACT

The present invention relates to a coating composition comprising 
     (A) at least one hydroxyl-containing component which [lacuna] of 
     (A1) from 5 to 60% by weight of at least one polyester and 
     (A2) from 40 to 95% by weight of at least one polyacrylate resin which has been prepared at least partially in the presence of component (A1) and 
     (B) at least one crosslinking agent, characterized in that component (A2) is obtainable from the monomer units: 
     (a) a cycloaliphatic ester of (meth)acrylic acid, 
     (b) a hydroxyl-containing alkyl ester of (meth)acrylic acid, 
     (c) a monomer which is different from (a) and (b) and has at least two polymerizable, olefinically unsaturated double bonds, 
     (d) optionally a further hydroxyl-containing, ethylenically unsaturated monomer which is different from (a), (b) and (c), 
     (e) an aliphatic ester of (meth)acrylic acid which is different from (a), (b), (c) and (d), 
     (f) a vinyl-aromatic hydrocarbon which is different from (a), (b), (c), (d) and (e), and 
     (g) a further ethylenically unsaturated monomer which is different from (a), (b), (c), (d), (e) and (f).

This application is the national stage of International Application No.PCT/EP97/03661, filed Jul. 10, 1997.

FIELD OF THE INVENTION

The present invention relates to a coating composition comprising

(A) at least one hydroxyl-containing component which comprises

(A1) from 5 to 60% by weight of at least one polyester and

(A2) from 40 to 95% by weight of at least one polyacrylate resin whichhas been prepared at least partially in the presence of component (A1)and which is obtainable from:

(a) a cycloaliphatic ester of methacrylic acid and/or acrylic acid, or amixture of such monomers,

(b) a hydroxyl-containing alkyl ester of methacrylic acid and/or acrylicacid, or mixtures of such monomers,

(c) a monomer which is different from (a) and (b) and has at least twopolymerizable, olefinically unsaturated double bonds,

(d) optionally a hydroxyl-containing, ethylenically unsaturated monomerwhich is different from (a), (b) and (c), or a mixture of such monomers,

(e) an aliphatic ester of methacrylic and/or acrylic acid which isdifferent from (a), (b), (c) and (d), or a mixture of such monomers,

(f) optionally a vinyl-aromatic hydrocarbon which is different from (a),(b), (c), (d) and (e), or a mixture of such monomers, and

(g) optionally a further ethylenically unsaturated monomer which isdifferent from (a), (b), (c), (d), (e) and (f), or a mixture of suchmonomers, and

(B) at least one crosslinking agent.

The present invention additionally relates to processes for producing amulticoat protective and/or decorative coating on a substrate surfaceand to the use of the coating compositions in the sector of automotiverefinishing.

BACKGROUND OF THE INVENTION

Coating compositions are already known, from DE-A-40 24 204, which asbinder contain a hydroxyl-containing polyacrylate resin which has beenprepared in the presence of a hydroxyl-containing polyester. Inparticular if these coating compositions are applied at lowtemperatures, the masking resistance and the solvent resistance of theresulting coatings are, however, in need of improvement.

Coating compositions based on hydroxyl-containing polyacrylate resinsand crosslinking agents are known, for example, from JP-A 4-1254. Inthis document, the hydroxyl-containing polyacrylate resins employed asbinders are obtainable from hydroxyl-containing monomers, alkylacrylates, alkyl methacrylates, optionally styrene and optionallyethylenically unsaturated polymers. In this case it is essential to theinvention that the polyacrylate resin has been prepared using4-tert-butylcyclohexyl acrylate and/or 4-tert-butylcyclohexylmethacrylate as monomer component. Hydroxyethyl acrylate and/orhydroxyethyl methacrylate, in particular, is employed ashydroxyl-containing monomer.

These coating compositions known from JP-A 4-1254, especially when usedas transparent topcoat over a basecoat film, have the particulardisadvantage that, when hydroxyethyl acrylate and/or hydroxyethylmethacrylate is used as OH monomer, the resulting coatings are ofinadequate adhesion to the basecoat film. A further disadvantage ofthese coating compositions known from JP-A 4-1254 is the inadequate potlife of the coating compositions.

EP-B-0 158 161 discloses hydroxyl-containing acrylate copolymersproduced by copolymerization of acrylate monomers having at least twoolefinically unsaturated double bonds, hydroxyl-containing monomers andfurther olefinically unsaturated monomers, which together withmelamine-formaldehyde resin as crosslinking agent can be employed ascoating compositions.

A feature of these coating compositions known from EP-B-0 158 161 aswell is that, especially when used as transparent topcoat over abasecoat film, they exhibit the disadvantage of resulting, whenhydroxyethyl(meth)acrylate is used as hydroxyl-containing monomer, incoatings having inadequate adhesion to the basecoat film, and that thepot life of the coating compositions is inadequate.

EP-A-0 638 591 describes hydroxyl-containing copolymers which can beprepared by a bulk polymerization in which one component is included inthe initial charge at the beginning of the polymerization and, in thesubsequent course of the polymerization, at least two olefinicallyunsaturated monomers are added, of which at least one contains at leastone carboxyl group and at least one is sterically hindered. Alsodescribed is the use of such copolymers in high-solids coatingcompositions. Again, the adhesion of such coating compositions inaccordance with EP-A 0 638 591 to basecoat films is inadequate.

DE-A 44 07 415 discloses coating compositions which provide anoutstanding solution to the problems resulting from the prior art todate. Such coating compositions include (A) at least onehydroxyl-containing polyacrylate resin, obtainable from (a) acycloaliphatic ester of (meth)acrylic acid, (b) a hydroxyl-containingester of (meth)acrylic acid, (c) optionally a hydroxyl-containing,ethylenically unsaturated monomer which is different from (a) and (b),(d) an aliphatic ester of (meth)acrylic acid which is different from(a), (b) and (c), (e) optionally a vinyl-aromatic hydrocarbon which isdifferent from (a), (b), (c) and (d), and (f) optionally a furtherethylenically unsaturated monomer which is different from (a), (b), (c),(d) and (e), and (B) at least one crosslinking agent.

When used as transparent topcoat over a pigmented basecoat film, thecoating compositions according to DE-A-44-07 415 exhibit markedlyimproved adhesion to the basecoat film coupled with good chemicalresistance and good weathering resistance. The coating compositions canbe cured at low temperatures and can therefore be employed for thesector of automotive refinishing, Even when the coating compositions arecured at these low temperatures, the coating compositions rapidly curefully but at the same time exhibit processability for a sufficientlylong period. Moreover, the coating compositions according to DE-A-44 07415 have the advantage of a good topcoat holdout, exhibit very good flowand good application properties under the conditions of automotiverefinishing, and, when used as clearcoat over a basecoat film, they donot start to dissolve this film to any great extent. Recent requirementsof the market necessitate, however, a level of adhesion which isimproved again over the coating compositions according to DE-A-44 07 415when the coating compositions are employed as clearcoat for the coatingof basecoat films, and necessitate a further-increased gasolineresistance and improved polishability.

SUMMARY OF THE INVENTION

The problem on which the present invention is based was therefore toprovide coating compositions which, when used as transparent topcoatover a pigmented basecoat film, lead to coatings having improvedadhesion to the basecoat and possessing improved gasoline resistance.

At the same time, the resulting coatings should be of good chemicalresistance and good weathering resistance. In addition, the coatingcompositions should be suitable for automotive refinishing, i.e. theyshould be fully curable at low temperatures of in general below 120degrees C, preferably below 80 degrees C. Furthermore, the coatingcompositions should also reach full cure (rapid dust dryness and freedomfrom tack, and rapid through-drying) at these low temperatures while atthe same time being able to be processed for as long (pot life) aspossible. In addition, the coating compositions should exhibit goodtopcoat holdout and, when used as clearcoat over a basecoat film, shouldcause only minimal dissolution of the underlying basecoat film andshould exhibit a good light/dark effect when viewed at different angles.Finally, the coating compositions should exhibit very good flow and goodapplication properties under the conditions of automotive refinishing.

This problem is surprisingly achieved by a coating composition of thetype mentioned initially, which is characterized in that component (A2)is a hydroxyl-containing component which is obtainable by polymerizingpreferably:

(a) from 5 to 80% by weight of component (a),

(b) from 10 to 50% by weight of component (b),

(c) from 1 to 25% by weight of component (c),

(d) from 0 to 25% by weight of component (d),

(e) from 5 to 80% by weight of component (e),

(f) from 0 to 40% by weight of component (f) and

(g) from 0 to 40% by weight of component (g)

at least partially in the presence of the polyester (A1) to give apolyacrylate resin (A2), component (A1) being present to the extent offrom 5 to 60% by weight and component (A2) to the extent of from 40 to95% by weight, based in each case on (A), and the sum of the proportionsby weight of components (a) to (g) always being 100% by weight, and themonomers or monomer mixtures employed as component (b) only being thosewhich, on polymerization of the respective monomer alone, produce apolyacrylate resin and/or polymethacrylate resin having a glasstransition temperature of from -10 to +6 degrees C or from +60 to 80degrees C.

The present invention additionally relates to a process for producing amulticoat coating on a substrate surface using these coatingcompositions, and to the use of the coating compositions in the sectorof automotive refinishing.

It is surprising and was not foreseeable that the novel coatingcompositions, when used as transparent topcoat over a pigmented basecoatfilm, exhibit markedly improved adhesion to the basecoat film while atthe same time having good gasoline resistance, good chemical resistanceand good weathering resistance. A further advantage is that the coatingcompositions can be cured fully at low temperatures and are suitable foruse in the sector of automotive refinishing. Even when the coatingcompositions are cured at these low temperatures the coatingcompositions rapidly attain full cure, although at the same time areable to be processed for a long time. Moreover, the novel coatingcompositions have the advantage of a good topcoat holdout and, under theconditions of automotive refinishing, show very good flow and goodapplication properties. Finally, when used as clearcoat over a basecoatfilm, the novel coating compositions have the advantage that they causeonly minor dissolution of the basecoat film and exert only a very smallinfluence on the metallic effect.

DETAILED DESCRIPTION OF THE INVENTION

The constituents of the coating composition

In the text below, the individual constituents of the novel coatingcomposition will now be described in more detail.

Component (A) of the coating composition

The polyester resin (A1)

The polyesters (A1) are preferably obtainable by reacting

(p1) polycarboxylic acids or their esterifiable derivatives, together ifdesired with monocarboxylic acids,

(p2) polyols, together if desired with monools,

(p3) optionally further modifying components, and

(p4) optionally a component which is reactive with the reaction productof (p1), (p2) and, if used, (p3).

Examples of polycarboxylic acids which may be employed as component (p1)are aromatic, aliphatic and cycloaliphatic polycarboxylic acids.

Examples of suitable polycarboxylic acids (p1) are phthalic acid,isophthalic acid, terephthalic acid, halophthalic acids, such astetrachloro- and tetrabromophthalic acid, adipic acid, glutaric acid,azelaic acid, sebacic acid, fumaric acid, maleic acid, trimellitic acid,pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid,1,2-, 1,3- and 1,4-cyclohexanedicarboxylic acid,4-methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid,tricyclodecanedicarboxylic acid, endoethylenehexahydrophthalic acid,camphoric acid, cyclohexanetetracarboxylic acid,cyclobutanetetracarboxylic acid and the like. The cycloaliphaticpolycarboxylic acids (p1) can be employed both in their cis form andtheir trans form and as a mixture of both forms. Also suitable are theesterifiable derivatives of the abovementioned polycarboxylic acids(p1), such as, for example, their mono- or polyesters with aliphaticalcohols having 1 to 4 carbon atoms or hydroxy alcohols having 1 to 4carbon atoms. It is additionally possible, as well, to employ theanhydrides of the abovementioned polycarboxylic acids (p1), providedthey exist.

If desired, it is possible together with the polycarboxylic acids (p1)to employ monocarboxylic acids as well, for example benzoic acid,tert-butylbenzoic acid, lauric acid, isononanoic acid and fatty acids ofnaturally occurring oils. A preferred monocarboxylic acid employed isisononanoic acid.

Suitable polyol components (p2) for the preparation of the polyester oralkyd resin (A1) are polyhydric alcohols, such as ethylene glycol,propanediols, butanediols, hexanediols, neopentyl glycol, diethyleneglycol, trimethylpentanediol, ethylbutylpropanediol, trimethylolpropane,ditrimethylolpropane, trimethylolethane, glycerol, pentaerythritol,dipentaerythritol, trishydroxyethyl isocyanate, polyethylene glycol,polypropylene glycol, together if desired with monohydric alcohols, forexample butanol, octanol, lauryl alcohol, ethoxylated and/orpropoxylated phenols.

Particularly suitable as component (p3) for the preparation of thepolyesters (A1) are compounds containing at least one group which isreactive toward the functional groups of the polyester, with theexception of the compounds mentioned as component (p4). As modifyingcomponent (p3) it is preferred to use polyisocyanates and/or diepoxidecompounds, and also, if desired, monoisocyanates and/or monoepoxidecompounds. Examples of suitable components (p3) are described in DE-A-4024 204 on page 4, lines 4 to 9.

As component (p4) for the preparation of the polyesters or alkyd resins(A1), suitable compounds are those having, in addition to a group whichis reactive toward the functional groups of the polyester (A1), atertiary amino group, examples being monoisocyanates having at least onetertiary amino group. For further details, reference is made to DE-A-4024 204, page 4, lines 10 to 49.

The polyesters (A1) are prepared by the known methods of esterification(compare various standard works, such as, for example:

1. Temple C. Patton, Alkyd Resin Technology, Interscience PublishersJohn Wiley & Sons, New York, London 1962;

2. Dr. Johannes Schreiber, Chemie und Technologie der kunstlichen Harze,Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, 1943;

3. Hans Wagner und Hans-Friedrich Sarx, Lackkunstharze, 4th Edition,Carl Hanser Verlag [sic], Munich, 1959;

4. Ullmanns Enzyklopadie der technischen Chemie, Volume 14, pages 80 to106, 1963).

This reaction is commonly carried out at temperatures between 180 and280 degrees C, optionally in the presence of an appropriateesterification catalyst, such as, for example, lithium octoate,dibutyltin oxide, dibutyltin dilaurate, p-toluenesulfonic acid and thelike.

The preparation of the polyesters (A1) is customarily carried out in thepresence of small quantities of an appropriate solvent as entrainingagent for the water produced in the reaction. Examples of entrainingagents employed are aromatic hydrocarbons, such as xylene in particular,and (cyclo)aliphatic hydrocarbons, especially cyclohexane.

The polyacrylate resin (A2) and the binder (A)

The polyacrylates employed as component (A2) in the novel coatingcompositions have OH numbers of from 60 to 180 mg of KOH/g, preferablyfrom 100 to 150 mg of KOH/g, and acid numbers from 0 to 30 mg of KOH/g,preferably from 0 to 15 mg of KOH/g, the OH numbers and the acid numberseach being calculated without taking into account the polyesterproportion.

It is essential to the invention that the polyacrylate resin (A2) hasbeen prepared at least partially in the presence of the polyester resin(A1). Advantageously at least 40% by weight, and particularlyadvantageously at least 50% by weight, of component (A2), are preparedin the presence of component (A1).

Any remaining quantity of component (A2) is added to the binder solutionand/or to the coating composition subsequently. In this case it ispossible for this already polymerized resin to have the same monomerstructural unit composition as the polyaddition resin synthesized in thepresence of the polycondensation resin. However, it is also possible toadd a hydroxyl-containing polyaddition resin and/or polycondensationresin which has a different monomer structural unit composition.Furthermore, it is possible to add a mixture of different polyadditionresins and/or polycondensation resins, in which optionally one resin hasthe same monomer composition as the polyaddition resin synthesized inthe presence of the polycondensation resin.

The polyacrylate resin (A2) employed in accordance with the invention ispreferably obtainable by polymerizing the components

(a) from 5 to 80% by weight, preferably from 5 to 30% by weight, of acycloaliphatic ester of methacrylic acid and/or acrylic acid, or of amixture of such monomers,

(b) from 10 to 50% by weight, preferably from 15 to 40% by weight, of ahydroxyl-containing alkyl ester of methacrylic acid and/or acrylic acid,or of a mixture of such monomers,

(c) from 1 to 25% by weight, preferably from 2 to 20% by weight, of amonomer which is different from (a) and (b) and has at least twopolymerizable, olefinically unsaturated double bonds,

(d) from 0 to 25% by weight, preferably from 0 to 15% by weight, of ahydroxyl-containing, ethylenically unsaturated monomer which isdifferent from (a), (b) and (c), or of a mixture of such monomers,

(e) from 5 to 80% by weight, preferably from 5 to 30% by weight, of analiphatic ester of methacrylic and/or acrylic acid which is differentfrom (a), (b), (c), (d) and (f), or of a mixture of such monomers,

(f) from 0 to 40% by weight, preferably from 10 to 30% by weight, of avinyl-aromatic hydrocarbon which is different from (a), (b), (c), (d),(e) and (g), or of a mixture of such monomers, and

(g) from 0 to 40% by weight, preferably from 0 to 30% by weight, of afurther ethylenically unsaturated monomer which is different from (a),(b), (c), (d), (e) and (f), or of a mixture of such monomers,

at least partially in the presence of the polyester resin (A1), to givea polyacrylate resin (A2) having an OH number of from 60 to 180,preferably from 100 to 150 mg of KOH/g, the sum of the proportions byweight of components (a) to (g) always being 100% by weight and themonomers or monomer mixtures employed as component (b) preferably onlybeing those which, on polymerization of the respective monomer alone,produce a polyacrylate resin and/or polymethacrylate resin having aglass transition temperature of from -10 to +6 degrees C or from +60 to80 degrees C.

The preparation of the polyacrylate resins (A2) employed in accordancewith the invention can be carried out in accordance with the generallywell-known polymerization techniques. Polymerization techniques forpreparing polyacrylate resins are generally known and described in manyreferences (compare for example: Houben-Weyl, Methoden der organischenChemie, 4th Edition, Volume 14/1, pages 24 to 255 (1961)).

The novel polyacrylate resins (A2) are preferably prepared with the aidof a solution polymerization technique. In this technique, an organicsolvent or solvent mixture is customarily charged to the reaction vesseltogether with the polyester (A1), and the mixture is heated to boiling.The monomer mixture (a) to (g) to be polymerized, of the polyacrylatecomponent (A2) and one or more polymerization initiators and one or morepolymerization regulators are then added continuously to said mixture oforganic solvent or solvent mixture and polyester resin (A1).

The polymerization of the monomer components (a) to (g) is preferablycarried out with the exclusion of oxygen, for example by working in anitrogen atmosphere. The reactor is equipped with appropriate stirring,heating and cooling devices and with a reflux condenser in whichvolatile constituents, for example styrene, are retained. Thepolymerization reaction is carried out at temperatures of from 100 to180 degrees C, preferably from 130 to 170 degrees C.

The polymerization is preferably carried out in a high-boiling organicsolvent which is inert with respect to the monomers employed. Examplesof suitable solvents are relatively highly substituted aromaticcompounds, for example Solvent Naphtha®, heavy benzene, variousSolvesso® grades, various Shellsol® grades and Deasol®, and alsorelatively high-boiling aliphatic and cycloaliphatic hydrocarbons, forexample various white spirits, mineral turpentine oil, tetralin anddecalin, and also various esters, for example ethylglycol acetate,butylglycol acetate, ethylglycol diacetate and the like.

As polymerization initiators it is preferred to employ initiators whichform free radicals. The nature and quantity of initiator are commonlychosen such that the supply of radicals present during the feed phase atthe polymerization temperature is as constant as possible. Examples ofinitiators suitable for the preparation of the polyacrylate resins (A2)are initiators containing tert-butyl groups, for example di-tert-butylperoxide, tert-butyl hydroperoxide, 2,2-di-tert-butylperoxybutane and1,3-bis-(tert-butylperoxyisopropyl-)-benzene, dibenzoyl peroxide,tert-butyl peroxy-2-ethylhexanoate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butyl peroxypivalate, tert-butylperacetate, tert-butyl cumene peroxide, other peroxides such as dicumylperoxide, cumyl peroxide, tert-amyl peroxybenzoate,tert-amylperoxy-2-ethylhexanoate, diacyl peroxides, for example diacetylperoxide, peroxyketals, 2,2-di-(tert-amylperoxy-) propane,ethyl-3,3-di-(tert-amylperoxy-)-butyrate, and thermally unstable highlysubstituted ethane derivatives, based for example on silyl-substitutedethane derivatives and based on benzopinacol. Furthermore, it is alsopossible to employ aliphatic azo compounds, for exampleazoisovaleronitrile and azobiscyclohexanenitrile.

The quantity of initiator is in most cases from 0.1 to 8% by weight,based on the quantity of monomers to be processed, but can if desiredalso be higher. The initiator, dissolved in a portion of the solventemployed for the polymerization, is metered in gradually during thepolymerization reaction. The initiator feed preferably lasts from about0.5 to 2 hours longer than the monomer feed in order, in this way, toobtain a good action during the after-polymerization phase as well. Ifinitiators are employed which have only a low decomposition rate underthe prevailing reaction conditions, then it is also possible to includethe initiator in the initial charge.

The polymerization regulators optionally present are employed inquantities of preferably at least 0.5% by weight, particularlypreferably at least 2.5% by weight, based on the overall weight of themonomers, such that the polyacrylate (A) is copolymerized to give aprecrosslinked, ungelled product. Examples of polymerization regulatorsemployed are compounds containing mercapto groups, for examplemercaptans or thioglycolic esters, or halogenated hydrocarbons.

The acid number of the polyacrylate resin (A2) is usually between 0 and30 mg of KOH/g, preferably between 0 and 15 mg of KOH/g. The acid numberof the polyacrylate resins employed in accordance with the invention canbe adjusted by the person skilled in the art by the use of appropriatequantities of component (g). Similar comments apply to the adjustment ofthe hydroxyl number. It can be controlled by way of a quantity ofcomponent (b) and (d) employed.

Examples of cycloaliphatic esters of acrylic acid and/or methacrylicacid which are suitable as components (a) are cyclohexyl acrylate,cyclohexyl methacrylate, 4-tert-butylcyclohexyl acrylate,4-tert-butylcyclohexyl methacrylate, isobornyl acrylate and isobornylmethacrylate. As component (a) it is particularly preferred to employ4-tert-butylcyclohexyl acrylate and/or 4-tert-butylcyclohexylmethacrylate.

It is preferred that the monomers or monomer mixtures employed ascomponent (b) are only those which, on polymerization of the respectivemonomer alone, produce a polyacrylate resin and/or polymethacrylateresin having a glass transition temperature of from -10 to +6 degrees C,or from +60 to 80 degrees C. This means that, when mixtures of differentmonomers are used as component (b), appropriate mixtures of courseinclude those which, on polymerization of component (b) alone, produce apolyacrylate resin and/or polymethacrylate resin having a TG value whichis outside these ranges indicated for the individual monomers.

The glass transition temperature can be calculated approximately by theperson skilled in the art with the aid of the formula ##EQU1## T_(G)=glass transition temperature of the polymer x=number of differentmonomers incorporated by polymerization,

W_(n) =proportion by weight of the nth monomer

T_(Gn) =glass transition temperature of the homopolymer of the nthmonomer.

Component (b) is preferably selected from 3-hydroxypropyl methacrylate,3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and/or2-hydroxypropyl acrylate.

Further suitable hydroxyl-containing monomers (component (d)) arehydroxyalkyl esters of alpha,beta-unaturated carboxylic acids containingprimary or secondary hydroxyl groups. If the acrylate copolymer isrequired to be of high reactivity, it is possible to employ exclusivelyhydroxyalkyl esters containing primary hydroxyl groups; if thepolyacrylate is to be less reactive, it is possible to employexclusively hydroxyalkyl esters containing secondary hydroxyl groups. Itis of course also possible to use mixtures of hydroxyalkyl esterscontaining primary hxydroxyl groups and hydroxyalkyl esters containingsecondary hydroxyl groups. Examples of suitable hydroxyalkyl esters ofalpha,beta-unsaturated carboxylic acids containing primary hydroxylgroups are hydroxybutyl acrylate, hydroxyamyl acrylate, hydroxyhexylacrylate, hydroxyoctyl acrylate and the corresponding methacrylates.Examples of hydroxyalkyl esters which can be used and which contain asecondary hydroxyl group are 2-hydroxybutyl acrylate, 3-hydroxybutylacrylate and the corresponding methacrylates. It is of course alsopossible in each case to employ the corresponding esters of otheralpha,beta-unsaturated carboxylic acids, for example those of crotonicacid and of isocrotonic acid.

Advantageously, component (d) may at least in part be a reaction productof one mol of hydroxyethyl acrylate and/or hydroxyethyl methacrylate andon average two mol of epsilon-caprolactone. The component (d) employedmay also be, at least in part, a reaction product of acrylic acid and/ormethacrylic acid with the equivalent quantity of a glycidyl ester of acarboxylic acid having a tertiary alpha carbon atom. Glycidyl esters ofhighly branched monocarboxylic acids are obtainable under the trade name"Cardura®". The reaction of the acrylic acid or methacrylic acid withthe glycidyl ester of a carboxylic acid having a tertiary alpha carbonatom can be carried out before, during or after the polymerizationreaction.

As component (c) it is preferred to employ compounds of the generalformula I ##STR1## where: R is H or methyl, X is 0, NH, NR₁ where R₁═C1-- to C10-alkyl, or S, and

n is 2 to 8.

Examples of such compounds are hexanediol diacrylate, hexanedioldimethacrylate, glycol diacrylate, glycol dimethacrylate, butanedioldiacrylate, butanediol dimethacrylate and similar compounds.

Component (c) may, furthermore, advantageously be a reaction product ofa carboxylic acid having a polymerizable, olefinically unsaturateddouble bond with glycidyl acrylate and/or glycidyl methacrylate, or apoly- or monocarboxylic acid which is esterified with an unsaturatedalcohol.

As component (c) it is also possible to employ aromatic compounds havingat least 2 substituents, which have polymerizable, olefinicallyunsaturated groups, such as preferably divinylbenzene.

Furthermore, diallyl compounds can be used as component (c).

In addition, it is possible advantageously to use as component (c) areaction product of a polyisocyanate with an unsaturated alcohol or withan unsaturated amine. An example hereof is the reaction product of 1 molof hexamethylene diisocyanate and 2 mol of allyl alcohol.

A further advantageous component (c) is a diester of polyethylene glycoland/or polypropylene glycol having an average molecular weight of lessthan 1500, preferably less than 1000 daltons, with acrylic acid and/ormethacrylic acid. In accordance with the invention it is possible ascomponent (c), also, to employ acrylates having more than twoethylenically unsaturated double bonds, such as, for example,trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,pentaerythritol tetraacrylate or pentaerythritol tetramethacrylate.

It is of course also possible to use combinations of thesepolyunsaturated monomers.

The monomers (e) employed in accordance with the invention arepreferably selected such that polymerization of component (e) aloneproduces a polyacrylate resin and/or polymethacrylate resin having aglass transition temperature of from -70 to 120 degrees C.

Examples of monomers suitable as component (e) are methyl(meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isopropyl(meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, isoamyl(meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,furfuryl (meth)acrylate, octyl (meth)acrylate, 3,5,5-trimethylhexyl(meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, hexadecyl(meth)acrylate, octadecyl (meth)acrylate, stearyl (meth)acrylate andethyltriglycol (meth)acrylate.

Vinyl-aromatic compounds are suitable as component (f) Component (f)preferably contains 8 to 9 carbon atoms per molecule. Examples ofsuitable compounds are styrene, vinyltoluenes, alpha-methylstyrene,chlorostyrenes, o-, m- or p-methylstyrene, 2,5-dimethylstyrene,p-methoxystyrene, p-tert-butylstyrene, p-dimethylaminostyrene,p-acetamidostyrene and m-vinylphenol. Preference is given to employingvinyltoluenes and, in particular, styrene.

Examples of compounds suitable as component (g) are unsaturatedcarboxylic acids, for example acrylic and/or methacrylic acid, maleicacid, fumaric acid, crotonic acid or isocrotonic acid, and also theanhydrides of these acids, alkoxyethyl acrylates, aryloxyethyl acrylatesand the corresponding methacrylates, for example butoxyethyl(meth)acrylate and phenoxyethyl (meth)acrylate, and alsomethacrylonitrile and acrylonitrile, and also alkyl esters of otherethylenically unsaturated carboxylic acids, for example alkyl esters ofcrotonic and isocrotonic acid, and also polymerizable vinyl ethers andvinyl esters.

It is preferred to add to binder component (A), following itspreparation, from 0.1 to 1% by weight, preferably from 0.4 to 0.9% byweight, of at least one aromatic mono- and/or polycarboxylic acid and/orat least one anhydride of an aromatic polycarboxylic acid. The quantityof acid and/or anhydride added in this case is based on the weight ofthe hydroxyl-containing binder (A), calculated as solid resin, in otherwords without solvent component. In this context it is preferred to addphthalic anhydride and monoesters of phthalic acid, benzoic acid and/oralkyl- and/or alkoxy-substituted benzoic acid. With particularpreference, benzoic acid is added. The acid is preferably added at atemperature of from 20 to 120 degrees C, particularly preferably at atemperature of from 40 to 100 degrees C. The addition of the anhydrideis preferably made at a temperature of from 100 to 180 degrees C,particularly preferably at a temperature of from 130 to 170 degrees C.In this case the acid and/or the anhydride can be added to the finishedcoating composition, in other words following the addition of pigments,fillers and auxiliaries and crosslinking agents. Preferably, however,the acid and/or the anhydride is added to the acrylate resin (A2) and isdistributed with maximum homogeneity.

The novel coating compositions may also, if desired, contain one or morefurther hydroxyl-containing resins. For example, they may containfurther hydroxyl-containing acrylate resins and/or polycondensationresins, different from constituents (A1) and (A2) of the novel bindercomponent (A). These further binders are normally employed in a quantityof from 0 to 25% by weight, preferably from 0 to 20% by weight, based ineach case on the overall weight of the coating composition and based onthe solids content of the binder.

Examples of suitable further binders are, for example, the polyacrylateresins which are obtainable commercially under the name Macrynal® SM 510and SM 513 from Hoechst, and the hydroxyl-containing polyacrylate resinswhich are described in German Patent Application DE-A-40 24 204 and areprepared in the presence of a polyester. For details, reference may bemade to DE-A-40 24 204, especially page 3, line 18 to page 7, line 53.

Another suitable example of a further binder is a hydroxyl-containingpolyacrylate resin which is obtainable by polymerizing

(m1) from 10 to 51% by weight of a mixture of

(m11) one or more monomers selected from the group 4-hydroxy-n-butylacrylate and/or 4-hydroxy-n-butyl methacrylate and/or 3-hydroxy-n-butylacrylate and/or 3-hydroxy-n-butyl methacrylate, and

(m12) one of more monomers selected from the group 3-hydroxy-n-propylacrylate and/or 3-hydroxy-n-propyl methacrylate and/or2-hydroxy-n-propyl acrylate and/or 2- hydroxy-n-propyl methacrylate,

(m2) from 0 to 20% by weight of a hydroxyl-containing ester of acrylicacid or of methacrylic acid having at least 5 carbon atoms in thealcohol residue, which ester-is different from (m1), or of a mixture ofsuch monomers,

(m3) from 28 to 85% by weight of an aliphatic or cycloaliphatic ester ofacrylic acid or of methacrylic acid having at least 4 carbon atoms inthe alcohol residue, which ester is different from (m1) and (m2), or ofa mixture of such monomers,

(m4) from 0 to 25% by weight of a vinyl-aromatic hydrocarbon which isdifferent from (m1), (m2) and (m3), or of a mixture of such monomers,

(m5) from 0 to 5% by weight of an ethylenically unsaturated carboxylicacid or of a mixture of ethylenically unsaturated carboxylic acids, and

(m6) from 0 to 20% by weight of an ethylenically unsaturated monomerwhich is different from (m1), (m2), (m3), (m4) and (m5), or of a mixtureof such monomers,

to give a polyacrylate resin having a hydroxyl number of from 60 to 200mg of KOH/g, an acid number of from 0 to 35 mg of KOH/g and anumber-average molecular weight of from 1000 to 5000, the sum of theproportions by weight of components (m1) to (m6) being in each case 100%by weight.

Examples of compounds suitable as monomer components (m1) to (m6) arethe compounds listed in connection with the description of the acrylateresin (A2).

The crosslinking agent (B)

The polyisocyanate component which is preferred as crosslinking agent(B) comprises any desired organic polyisocyanates having free isocyanategroups attached to aliphatic, cycloaliphatic, araliphatic and/oraromatic structures. It is preferred to employ polyisocyanates having 2to 5 isocyanate groups per molecule. If desired, small quantities oforganic solvent, preferably from 1 to 256 by weight based on purepolyisocyanate, may be added to the polyisocyanates so as to improve theease of incorporation of the isocyanate. Examples of suitable solventadditives for the polyisocyanates are ethoxyethyl propionate, butylacetate and the like.

Examples of suitable isocyanates are described, for example, in"Methoden der organischen Chemie", Houben-Weyl, Volume 14/2, 4thEdition, Georg Thieme Verlag, Stuttgart 1963, page 61 to 70, and by W.Siefken, Liebigs Ann. Chem. 562, 75 to 136. Suitable examples are1,2-ethylene diisocyanate, 1,4-tetramethylene diisocyanate,1,6-hexamethylene diisocyanate, 2,2,4- and/or2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecanediisocyanate, omega, omega'-diisocyanatodipropyl ether,cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate,2,2- and 2,6-diisocyanato-1-methylcyclohexane,3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate ("isophoronediusocyanate"), 2,5- and3,5-bis(isocyanatomethyl)-8-methyl-1,4-methanedecahydronaphthalene[sic], 1,5-, 2,5-, 1,6- and2,6-bis(isocyanatomethyl)-4,7-methanehexahydroindane [sic], 1,5-, 2,5-,1,6- and 2,6-bis(isocyanato)-4,7-methanehexahydroindane [sic]dicyclohexyl-2,4'- and -4,4'-diisocyanate, 2,4- and2,6-hexahydrotolylene diisocyanate, perhydro-2,4'- and-4,4'-diphenylmethane diisocyanate,ω,ω'-diisocyanato-1,4-diethylbenzene, 1,3- and1,4-phenylenediisocyanate, 4,4'-diisocyanatobiphenyl,4,4'-diisocyanato-3,3'-dichlorobiphenyl,4,4'-diisocyanato-3,3'-dimethoxybiphenyl,4,4'-diisocyanato-3,3'-dimethyl-biphenyl,4,4'-diisocyanato-3,3'-diphenyl-biphenyl, 2,4'- and4,4'-diisocyanato-diphenylmethane, naphthylene-1,5-diisocyanate,tolylene diisocyanates, such as 2,4- and/or 2,6-tolylene diisocyanate,N,N'-(4,4'-dimethyl-3,3'-diisocyanatodiphenyl)-uretdione, m-xylylenediisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylenediisocyanate, but also triisocyanates, such as2,4,4'-triisocyanatodiphenyl ether,4,4',4"-triisocyanato-triphenylmethane.

Preference is given to employing, in combination if desired with theabovementioned polyisocyanates, polyisocyanates which containisocyanurate groups and/or biuret groups and/or allophanate groupsand/or urethane groups and/or urea groups. Polyisocyanates containingurethane groups, for example, are obtained by reacting some of theisocyanate groups with polyols, for example trimethylolpropane andglycerol.

It is preferred to employ aliphatic or cycloaliphatic polyisocyanates,especially hexamethylene diisocyanate, dimerized and trimerizedhexamethylene diisocyanate, isophorone diisocyanate,dicyclohexylmethane-2,4'-diisocyanate ordicyclohexylmethane-4,4'-diisocyanate, or mixtures of thesepolyisocyanates. It is very particularly preferred to employ mixtures ofpolyisocyanates which are based on hexamethylene diisocyanate andcontain uretdione and/or isocyanurate groups and/or allophanate groups,as are formed by catalytic oligomerization of hexamethylene diisocyanateusing appropriate catalysts. The polyisocyanate component (B) mayadditionally comprise any desired mixtures of the polyisocyanatesmentioned by way of example.

The quantity of the preferably employed crosslinking agent (B) is chosensuch that the ratio of the isocyanate groups of the crosslinking agentto the hydroxyl groups of the binder component is in the range from 1:3to 3:1. The novel coating compositions usually contain from 15 to 50% byweight of the polyester-modified acrylate resin (A), from 0 to 25% byweight of the further binder component and from 7 to 50% by weight ofthe crosslinking agent (B), based in each case on the overall weight ofthe coating composition and based on the solids content of the bindercomponents and crosslinking components.

Other components of the novel coating composition

The novel coating compositions additionally contain one or more organicsolvent. These solvents are usually employed in quantities of from 20 to70% by weight, preferably from 30 to 60% by weight, based in each caseon the overall weight of the coating composition. Examples of suitablesolvents are relatively highly substituted aromatic compounds, forexample Solvent Naphtha®, heavy benzene, various Solvesso® grades,various Shellsol® grades and Deasol®, and also relatively high-boilingaliphatic and cycloaliphatic hydrocarbons, for example various whitespirits, mineral turpentine oil, tetralin and decalin and also variousesters, for example ethylglycol acetate, butylglycol acetate,ethyldiglycol acetate and the like.

The novel coating compositions may additionally contain customaryauxiliaries and additives in customary quantities, preferably from 0.01to 10% by weight based on the overall weight of the coating composition.Examples of suitable auxiliaries and additives are leveling agents, suchas silicone oils, plasticizers, such as phosphates and phthalates,viscosity-controlling additives, matting agents, UV absorbers, lightstabilizers and, if desired, fillers.

Furthermore, the novel coating compositions may also contain customarypigments in customary quantities, preferably from 0 to 40% by weightbased on the overall weight of the coating composition. Examples ofsuitable pigments are organic and inorganic color pigments and alsometal pigments and/or special-effect pigments.

The preparation and the use of coating compositions

The coating compositions are prepared in a known manner by mixing and,if appropriate, dispersing the individual components.

These coating compositions can be applied in the form of a film to asubstrate by a spraying, flowcoating, dipping, rolling, knife coating orspreading, the film subsequently being cured to give a firmly adheringcoating.

These coating compositions are conventionally cured at room temperatureor slightly elevated temperature, advantageously at temperatures below120 degrees C, preferably at temperatures below 80 degrees C. However,the coating compositions can also be cured under baking conditions, inother words temperatures of at least 120 degrees C.

Suitable substrates are, in particular, metals and also wood, plastic,glass and the like. Owing to the short curing times and low curingtemperatures, the novel coating compositions are preferably used forautomotive refinishing, the finishing of large-size vehicles and truckbodies. However, depending on the crosslinking agent employed, they mayalso be employed for the production-line finishing of automobiles.Moreover, they are suitable as a pigment-containing solid-color topcoat.However, they are preferably employed as clearcoat especially over ametallic basecoat film or a solid-color basecoat film.

The present invention therefore also relates to a process for producinga multicoat protective and/or decorative coating on a substrate surface,in which

(1) a pigmented basecoat is applied to the substrate surface,

(2) a polymer film is formed from the basecoat applied in stage (1),

(3) to the basecoat thus obtained there is applied a transparent topcoatcontaining

(A) a hydroxyl-containing component and

(B) a crosslinking agent, and subsequently

(4) basecoat film and topcoat film are cured together, characterized inthat the topcoat employed is the novel coating composition.

The basecoats employed in this process are known and therefore requireno more detailed description. Examples of suitable basecoats are alsothe basecoats described in DE-A-41 10 520, in DE-A-40 09 000, in DE-A-4024 204, in EP-A-355 433, in DE-A-35 45 618, in DE-A-38 13 866 and inDE-A-42 32 717.

Also suitable are the basecoats described in DE-A-43 27 416, which arecharacterized in that they contain a hydroxyl-containing polyesterhaving a weight-average molecular weight Mw of 40,000-200,000 daltonsand a polydispersity Mw/Mn>8, and in that the polyester has beenprepared using at least 50% by weight of aromatic dicarboxylic acids ortheir esterifiable derivatives, but where the content of phthalicanhydride is no more than 80% by weight and the percentages by weightare based in each case on the overall weight of the acid componentsemployed for the preparation of the polyester.

The novel coating compositions are particularly notable for goodadhesion to the basecoat film, good mar resistance and high hardness ofthe resulting coatings. In addition, the coating compositions exhibitrapid drying coupled with long processability (pot life). Moreover, theresulting coatings, especially in the case of clearcoats, display goodmechanical properties such as, for example, good gloss retention, goodfullness and good leveling.

The invention will now be illustrated in more detail with reference toworking examples. In these examples all parts and percentages are byweight unless expressly stated otherwise.

EXAMPLES

1. Preparation of polyester component A1

1.1. Preparation of a polyester resin A11

1229 parts of trimethylolpropane, 832 parts of isononanoic acid, 1295parts of 1,4-cyclohexanedicarboxylic acid and 140 parts of xylene areplaced in a 41 polycondensation reactor with stirrer, steam-heatedcolumn and water separator, and are slowly heated. Condensation iscarried out at a maximum temperature of 202 degrees C to an acid numberof 10 mg of KOH/g and a viscosity of 4.2 dPas (60%i strength in xylene).The mixture is subsequently cooled, diluted at 130 degrees C with 1427parts of Shellsol® A, and cooled further to room temperature. Theresulting polyester A11 has a solids content of 63.2%, an acid number of10.3 mg of KOH/g, a (theoretical) OH number of 143.1 mg of KOH/g and aviscosity of 16.0 dPas (original). The number-average molecular weightMn is 1500 daltons, the weight-average molecular weight Mw is 3500daltons and the polydispersity Mw/Mn is 2.3 (determined in each case bygel permeation chromatography against polystyrene standard).

1.2. Preparation of a polyester resin A12

419 parts of trimethylolpropane, 325 parts of neopentyl glycol, 805parts of neopentylglycol hydroxypivalate, 315 parts of isophthalic acid,642 parts of hexahydrophthalic anhydride, 179 parts of adipic acid, 0.8parts of catalyst (Fascat® 4100 from Atochem) and 104 parts of xyleneare placed in a 41 polycondensation reactor with stirrer, steam-heatedcolumn and water separator, and are slowly heated. Condensation iscarried out at a maximum temperature of 208 degrees C to an acid numberof 4.7 mg of KOH/g and a viscosity of 1.2 dPas (60% strength in xylene).The mixture is subsequently cooled, diluted at 130 degrees C with 730parts of Shellsol® A, and cooled further to room temperature.

The resulting polyester A12 has a solids content of 75.0%, an acidnumber of 4.7 mg of KOH/g, a (theoretical) OH number of 204.1 mg ofKOH/g and a viscosity of 3.5 dPas (60% strength solution in Shellsol®A). The number-average molecular weight Mn is 1100 daltons, theweight-average molecular weight Mw is 2600 daltons and thepolydispersity Mw/Mn is 2.36 (determined in each case by gel permeationchromatography against polystyrene standard).

2. Preparation of the novel polyester-modified hydroxyl-containingbinder component A and also of a polyester-modified binder component V(without monomer (c) in the polyacrylate) as comparison example

The preparation of the novel hydroxyl-containing polyester-modifiedcomponent A and of the polyester-modified binder component V ascomparison is carried out in each case in a 41 stainless-steelpolymerization vessel with stirrer, reflux condenser, a monomer feed andan initiator feed. The components indicated in each case in Table 1 areweighed in and then the initial charge is heated to 145 to 152 degreesC.

All feeds are begun simultaneously; the monomer feed is metered in at auniform rate over the course of 4 hours, the initiator feed is meteredin at a uniform rate over the course of 4.5 hours. During polymerizationthe temperature in the reactor is held at 145 to 152 degrees C. This isfollowed by after-polymerization for 2 hours more. The acrylate resinsolution thus obtained has a solids content of 70%. The temperature issubsequently lowered to 110 degrees C and the acrylate resin is-dilutedwith butyl acetate to a solids content of 60%.

The quantities of the polyester resin A11 or A12 indicated in each casein Table 1, and also the quantity of Shellsol® A indicated in Table 1,are weighed into the initial charge.

The quantities of styrene, methyl methacrylate, hexanediol(meth)acrylate, 4-tert-butylcyclohexyl acrylate, butyl methacrylate,hyroxypropyl [sic] methacrylate indicated in each case in Table 1, andin each case the indicated quantities of triisodecyl phosphite andmercaptoethanol, are weighed into the monomer feed.

In the preparation of the novel binder component A, 3.13 parts oftert-butyl peroxyethylhexanoate and 5.53 parts of Shellsol® A areweighed into the initiator feed.

In the preparation of the binder component V, 1.17 parts of tert-butylcumyl hydroperoxide and 5.23 parts of Shellsol® A (commerciallyavailable aromatic solvent mixture having a boiling range from 165 to185 degrees C) are weighed into the initiator feed.

The properties of the resulting binder components A and V (comparison)are shown in Table 2.

3. Preparation of the coating compositions containing the bindersaccording to Example 2

3.1. Preparation of a curing agent solution

A curing agent solution is prepared from the components indicated below,by mixing:

    ______________________________________                                        butyl acetate 98%       1.5 parts                                             xylene                  7.5 parts                                             butylglycol acetate     11.0 parts                                            catalyst solution.sup.1 4.0 parts                                             Desmodur ® N 3390.sup.2                                                                           50.6 parts                                            Solventnaphtha ®    10.0 parts                                            Baysilon ® Lackadditiv OL44.sup.3                                                                 0.6 parts                                             i-methoxypropyl 2-acetate                                                                             14.0 parts                                            ______________________________________                                         .sup.1 catalyst solution described under section 3.3                          .sup.2 commercial polyisocyanate from Bayer AG, a 90% strength solution i     butyl acetate/solvent naphtha 1:1 based on a hexamethylene diisocyanate       trimer having a numberaverage molecular weight Mn of about 700 daltons, a     mean functionality of between 3 and 4 and a content of uretdione groups o     between 0 and 5% by weight                                                    .sup.3 commercial leveling agent based on a polyethermodified                 methylpolysiloxane, from Bayer AG                                        

3.2. Preparation of an adjustment additive

An adjustment additive is prepared from the components indicated below,by mixing:

    ______________________________________                                        xylene                 15.0 parts                                             Naphtha ®solvent   13.0 parts                                             petroleum spirit 135/180                                                                             10.0 parts                                             butylglycol acetate    3.0 parts                                              butyl acetate (98/100) 50.0 parts                                             1-methoxypropyl 2-acetate                                                                            5.0 parts                                              butoxyl                2.0 parts                                              ______________________________________                                    

3.3. Preparation of a catalyst solution

1.0 parts of dibutyltin dilaurate are mixed with 50.0 parts of butylacetate 98/100 and 49.0 parts of xylene.

3.4. Preparation of the clearcoat solutions KA and KV (comparisonexample)

The clearcoat solutions KA (according to the invention) and KV(comparison) are prepared from the components indicated in Table 3, bymixing.

3.5. Preparation of the transparent topcoats KA' and KV' (comparisonexample)

The transparent topcoats KA' and KV' are prepared by mixing in each case100 parts by volume of the clearcoat solutions KA and, respectively, KVwith 50 parts by volume of the above-described curing agent solution(Example 3.1) and 10 parts by volume of the above-described adjustmentadditive (Example 3.2).

The coating material obtained in this way is then applied tophosphatized and coated steel panels. For this purpose the phosphatizedsteel panels are coated by spraying with a conventional commercialfiller (commercial product Glasurit Grundfuller [primer surfacer] EP801-1552 from Glasurit GmbH, Munster, with an epoxy-functional binderand an amino-functional curing agent) (dry film thickness from about 40to 60 μm), dried at 80 degrees C for 45 minutes and at room temperaturefor 16 h, and sanded with P800 sandpaper and an eccentric sander.Subsequently, a basecoat is applied which comprises a mixture of 80parts of conventional commercial metallic basecoat (commercial productBasislack [basecoat] AE 54M 99/9 Basisfarbe Aluminium superfein fromGlasurit GmbH, Munster) based on a hydroxyl-containing polyester,cellulose acetobutyrate, wax and a melamine resin, and 20 parts of afurther conventional commercial basecoat (commercial product Basislack[basecoat] AE 54M 552 Basisfarbe Helioblau from Glasurit GmbH, Munster)based on a hydroxyl-containing polyester, cellulose acetobutyrate, waxand a melamine resin, by first of all applying one spraypass and, afteran intermediate flash-off time of 5 minutes, applying a second spraypass(spray pressure in each case 4 to 5 bar). The dry film thickness of thebasecoat is about 20 μm. After a flash-off time of 30 minutes theclearcoat is applied by first of all applying one spraypass and, afteran intermediate flash-off time of 3 minutes, applying a second spraypass(spray pressure in each case 4 to 5 bar). The panels are then driedunder different conditions depending on the test carried out. The dryfilm thickness of the clearcoat is from about 50 to 80 μm.

The results of testing of the resulting coatings are shown in Table 4.

                  TABLE 1                                                         ______________________________________                                        Composition of components A and V                                             Constituents of the binder                                                                          A      V                                                ______________________________________                                        A11 (polyester acc. to Ex. 1.1)                                                                     6.69                                                    A12 (polyester acc. to Ex. 1.2)                                                                            7.79                                             Shellsol A            17.69  18.51                                            Styrene               11.99  12.08                                            n-butyl methacrylate  3.13   3.15                                             t-butylcyclohexyl acrylate                                                                          7.31   7.35                                             methyl methacrylate   8.89   11.03                                            hydroxy-n-propyl acrylate                                                                           18.79  18.91                                            25% by weight of 3-hydoxy-                                                    [sic]/75% by weight of 2-hydroxy-                                             n-propyl acrylate                                                             hexanediol diacrylate 2.09   --                                               mercaptoethanol       0.254  0.26                                             triisodecyl phosphite 0.135  0.14                                             ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Properties of components A and V                                                                 A(1) V1                                                    ______________________________________                                        OH number [mg of KOH/g]                                                                            130    134                                               acid number [mg of KOH/g]                                                                          2.8    2.3                                               solids content [%]   59.4   61.3                                              Viscosity.sup.1 [dPas]                                                                             1.7    2.5                                               ______________________________________                                         .sup.1 Viscosity of a 50% strength solution of the acrylate resin in buty     acetate at 23 degrees C.                                                 

                  TABLE 3                                                         ______________________________________                                        Composition of the clearcoat solutions in                                     parts by weight                                                               Clearcoat solution                                                                              KA     KV                                                   ______________________________________                                        A.sup.1           87.0   --                                                   V1.sup.1          --     87.0                                                 LS1.sup.2         0.9    0.9                                                  LS2.sup.3         0.9    0.9                                                  DBTL.sup.4        2.0    2.0                                                  LAS.sup.5         3.8    3.8                                                  BGA.sup.6         2.4    2.4                                                  BA.sup.7          3.0    3.0                                                  SC(%).sup.8       52.2   52.2                                                 ______________________________________                                         Key to Table 3                                                                .sup.1 solutions described in Table 1 of the binder components A              (according to the invention) and V (comparison), all of which have howeve     been adjusted with butyl acetate to a uniform solids content of 58%           .sup.2 Tinuvin ® 292 from Ciba Geigy, commercial light stabilizer         based on a sterically hindered amine (HALS)                                   .sup.3 Tinuvin ® 1130 from Ciba Geigy, commercial light stabilizer        based on benzotriazole                                                        .sup.4 catalyst solution according to Example 3.3                             .sup.5 leveling agent solution according to Example 3.4                       .sup.6 butylglycol acetate                                                    .sup.7 butyl acetate 98% strength                                             .sup.8 Solids content                                                    

                  TABLE 4                                                         ______________________________________                                        Test results of the applied topcoats KA'                                      (novel) and KV' (comparison)                                                                KA'       KV'                                                   ______________________________________                                        appl. topcoat                                                                 Adhesion        16          20                                                Viscosity (s)   20          20                                                after 2h        29          27                                                dust dry (min)  90          110                                               tack-free (min) 240         290                                               gasoline test (days)                                                                          8           16                                                Volvo test      m0/g0       m0/g0                                             color (comparison)                                                            viewed straight on                                                                            identical   identical                                         viewed at an angle                                                                            identical   identical                                         assessment      satisfactory                                                                              satisfactory                                      ______________________________________                                    

Key to Table 4

The tests indicated in Table 4 are carried out as follows:

Adhesion: Testing with the high-pressure cleaner:

High-pressure cleaner

80 bar pressure

throughput 8001/h

temperature: cold

distance of the nozzle from the test panel: 5 cm

The test coating material is applied as described in Example 3.5 to a40×60 cm steel panel and dried at 60 degrees C for 30 minutes. Followingstorage at room temperature for 7 days, a knife is used to cut atriangle whose sides are 10 cm long through the coats of paint. The cutmust be made to the substrate. The sides of the triangle aresubsequently subjected to the jet of the high-pressure cleaner for 10 sin each case. Evaluation: a metal lattice, cut in squares, with a meshsize of 1/2 inch (1.3 cm) and a total edge length of 6 inches (15.4 cm)is placed over the triangle (144 squares). A count is made of eachsquare in which there is a loss of adhesion between clearcoat andbasecoat.

Viscosity:

The viscosity is measured in each case with the flow time in the DIN 4cup at 20 degrees C.

Dust dryness:

About 15 minutes after the application of the coating material byspraying, a small sample of marine sand (3 to 4 g) is scattered on onecorner of the panel. The panel is then dropped on one edge from a heightof 30 cm (free fall). Dust dryness is attained when no sand adheres. Thetest is repeated at 15-minute intervals; shortly before dust dryness isattained the repetition interval is shortened to 5 minutes.

Freedom from tack:

About 20 minutes after dust dryness has been attained, a piece of paperof about 3cm² is placed on the coated panel. A small plate of hardplastic is placed on this paper, and a weight of 100 g is then placed onthis plate. After precisely 1 minute, testing is carried out as in thetest for dust dryness, to see whether the paper still adheres. Testingis repeated at 15-minute intervals; shortly before freedom from tack isattained, the repetition interval is shortened to 5 minutes.

Gasoline test:

As described above, the clearcoat is applied to phosphatized, coatedsteel panels which are coated with the above-described filler andbasecoat, and dried at room temperature. The gasoline resistance isfirst tested after storage at room temperature for 24 hours.

Procedure: a wadding pad (filter grade, type T950, size 2.3 from Seitz)impregnated with 1 ml of premium-grade gasoline (lead-free), and whosebottom face possesses a lattice structure, is laid on the coat of paintand subjected for 5 minutes to a weight of 100 g. The structure broughtabout by the swelling-up of the paint surface is then assessed visually:not marked, very slightly marked, slightly marked, marked, heavilymarked, very heavily marked. The value indicated is the period ofstorage at room temperature, in days, after which the gasoline test issatisfactory, i.e. no marking is visible.

Volvo test:

Test conditions 1 cycle:

4 h at 50 degrees C in an oven

2 h at 35 degrees C and 95-100% rel. atmospheric humidity

2 h at 35 degrees 95-100% rel. atmospheric humidity and 21 of sulfurdioxide

16 h at -30 degrees in a deep-freeze cabinet wash panel with water anddry

Evaluation:

degree of blistering in accordance with DIN 53209 cracks ASTM D660

Color in accordance with DIN 6174:

Standard light source D

3 angle measuring instrument MMK111, Datacolor

The base color used was a mixture of the commercial base colors fromBASF L+F, (Munster-Hiltrup, Germany) series 54. A mixture of 80 parts byweight 54M 99/9 Basisfarbe Aluminium superfein and 20 parts by weight54M 552 Basisfarbe Helioblau was employed. The test coating material isapplied as described in section II.6. [sic] to a 40×60 cm steel paneland dried at 60 degrees C for 30 minutes. After storage at roomtemperature for 24 hours, the color test is carried out.

The panels are assessed under an Osram Universal white neon lamp:

1. Viewed straight on: the panels are compared with standard panel(coated with the clearcoat KA or KV) at an angle of about 20 degrees tothe vertical.

2. Viewed at an angle: the panels are compared with the standard panel(coated with a clearcoat KA or KV) at an angle of about 70 degrees tothe vertical.

Evaluation:

The light/dark change between the straight-on view and angular viewshould be as pronounced as possible. The straight-on view issatisfactory if the panel with the test clearcoat is of equal lightnessto or greater lightness than the standard panel. The angular view issatisfactory if the panel with the test coating material is of equallightness to or lesser lightness than the standard panel.

What is claimed is:
 1. A coating composition comprising at least onehydroxyl-containing binder component (A) consisting of:(A1) from 5 to60% by weight of at least one polyester and (A2) from 40 to 95% byweight of at least one polyacrylate which has been prepared at leastpartially in the presence of the polyester (A1), and (B) at least onecrosslinking agent, characterized in that component (A2) results fromthe polymerization of the monomer units: (a) one or more monomersselected from the group consisting of a cycloaliphatic ester ofmethacrylic acid, a cycloaliphatic ester of acrylic acid, and a mixtureof such monomers, (b) one or more monomers selected from the groupconsisting of a hydroxyl-containing alkyl ester of methacrylic acid, ahydroxyl-containing alkyl ester of acrylic acid, and mixtures of suchmonomers, (c) one or more monomers which are selected from thosemonomers which are different from (a) and (b) and have at least twopolymerizable, olefinically unsaturated double bonds, and mixturesthereof, (d) optionally, one or more hydroxyl-containing ethylenicallyunsaturated monomers which are different from (a), (b), (c), or amixture of such monomers, (e) one or more monomers which are differentfrom (a), (b), (c), and (d) and are selected from the group consistingof an aliphatic ester of methacrylic acid, an aliphatic ester ofacrylicacid and a mixture of such monomers, (f) optionally a vinyl-aromatichydrocarbon which is different from (a), (b), (c), (d) and (e), or amixture of such monomers, and (g) optionally a further ethylenicallyunsaturated monomer which is different from (a), (b), (c), (d), (e), and(f), or a mixture of such monomers.
 2. The coating composition of claim1, comprising polyacrylate (A2) resulting from the polymerization of:(a)from 5 to 80% by weight of component (a), (b) from 10 to 50% by weightof component (b), (c) from 1 to 25% by weight of component (c), (d) from0 to 25% by weight of component (d), (e) from 5 to 80% by weight ofcomponent (e), (f) from 0 to 40% by weight of component (f), and (g)from 0 to 40% by weight of component (g)to give a polyacrylate resin(A2) having an OH number of from 60 to 180 mg of KOH/g, the sum of theproportions by weight of components (a) to (g) always being 100% byweight.
 3. The coating composition of claim 1, characterized in that themonomers or monomer mixtures employed as component (b) only are thosewhich, on polymerization of the respective monomer alone, produce apolyacrylate resin and/or polymethacrylate resin having a glasstransition temperature of from -10 to +6 degrees C or from +60 to 80degrees C.
 4. The coating composition of claim 3, characterized in thatcomponent (b) is selected from the group consisting of 3-hydroxypropylmethacrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,2-hydroxypropyl acrylate, and mixtures thereof.
 5. The coatingcomposition of claim 1, wherein component (c) comprises ##STR2## where:R is H or methyl, x is O, NH, NR₁ where R₁ ═C1-- to C10-- alkyl, or S,andn is 2 to
 8. 6. The coating composition of claim 1, characterized inthat component (d) is selected such that polymerization of component (d)alone produces a polyacrylate resin and/or polymethacrylate resin havinga glass transition temperature of from -70 to +120 degrees C°.
 7. Thecoating composition of claim 6, characterized in that component (d) isselected from the group consisting of n-butyl methacrylate, n-butylacrylate, tert-butyl methacrylate, tert-butyl acrylate, isobutylmethacrylate, isobutyl acrylate, methyl methacrylate, methyl acrylate,2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate,lauryl acrylate, stearyl methacrylate, stearyl acrylate, ethyltriglycolmethacrylate, furfuryl methacrylate, furfuryl acrylate, and mixturesthereof.
 8. The coating composition of claim 1, wherein component (a) isselected from the group consisting of cyclohexyl methacrylate,cyclohexyl acrylate, isobornyl methacrylate, isobornyl acrylate,4-tert-butylcyclohexyl acrylate, 4-tert-butylcyclohexyl methacrylate andand mixtures thereof.
 9. The coating composition of claim 2, whereinpolyacrylate resin (A2) is obtained by polymerizing:(a) from 5 to 30% byweight of component (a), (b) from 15 to 40% by weight of component (b),(c) from 2 to 20% by weight of component (c), (d) from 0 to 15% byweight of component (d), (e) from 5 to 30% by weight of component (e),(f) from 10 to 30% by weight of component (f), and (g) from 0 to 30% byweight of component (g)the sum of the proportions by weight ofcomponents (a) to (g) being always 100% by weight.
 10. The coatingcomposition of claim 1, characterized in that polyacrylate resin (A2)has an OH number of from 100 to 150 mg of KOH/g.
 11. The coatingcomposition of claim 1, characterized in that the polyester (A1) has anOH number of from 90 to 130, an acid number of less than 30 mg of KOH/gand a number-average molecular weight Mn of from 1000 to 3500 daltons.12. The coating composition of claim 1, further comprising from 0.1 to1% by weight, based on the weight of component (A) without solvents, ofat least one member selected from the group consisting of an aromaticmono carboxylic acid, an aromatic polycarboxylic acid, an anhydride ofan aromatic carboxylic acid, or mixtures thereof.
 13. The coatingcomposition of claim 1, characterized in that at least 40% by weight ofcomponent (A2) has been prepared in the presence of component (A1). 14.The coating composition of claim 1, characterized in that the coatingcomposition contains as crosslinking agent (B) a member selected fromthe group consisting of diisocyanates, polyisocyanates, and mixturesthereof.
 15. The coating composition of claim 1 further comprising atleast one further binder which is different from component (A).
 16. Aprocess for the production of a multicoat protective and/or decorativecoating on a substrate surface, comprising(1) applying a pigmentedbasecoat to a substrate surface, (2) forming a polymer film from thepigmented basecoat applied in (1), (3) applying to the polymer film thusobtained a transparent topcoat containing the novel binder component (A)and a crosslinking agent (B), and (4) curing the polymer film andapplied transparent topcoat together.
 17. A process for the repair of apreviously cured coated substrate, comprising applying to a previouslycured coated substrate the coating composition of claim
 1. 18. Thecoating composition of claim 8, wherein component (a) is selected fromthe group consisting of 4-tert-butylcyclohexyl acrylate,4-tert-butylcyclohexyl methacrylate, and mixtures thereof.
 19. Thecoating composition of claim 14 characterized in that the coatingcomposition contains as crosslinking agent (B) at least one memberselected from the group consisting of diisocyanates containing one ormore isocyanurate groups, polyisocyanates containing one or moreisocyanurate groups, and mixtures thereof.
 20. The coating compositionof claim 15 further comprising at least one further binder selected fromthe group consisting of at least one further polyacrylate resin which isdifferent from (A2), at least one polycondensation resin which isdifferent from (A1), and mixtures thereof.